Vapor generator



June 30, 1942.

R. M. HARDGROVE ET AL VAPOR GENERATOR 4 Sheets-Sheet l Filed Aug. 3,1938 Poberi K ehr 1' [pk M Hardyrove.

1942- R. M. HARDGROVE EI'AL 2,287,798

VAPOR GENERATOR Filed Aug. 3, 1958 4 Sheets-Sheet 2 Fi :2 e2

I ll

1. m1 1 Fr Economizer 102 Inle Primary Economizer Super/Heater Outlet l18 INVENTORS Eober! K Behr BE 1217? 11j fa myrm e v I I 'I t; ATTORNEY.

J1me 1942- R. M. HARDGROVE ETAL 2,287,798

VAPOR GENE RATOR Filed Aug. 3, 1938 4 Sheets-Sheet 3 INVENTORS Faberi K58/71" 1 4 M Hardy/ave n 30,1942. R. M. HARDGRQVE Em 2,287,198

' VAPOR GENERATOR Filed Au 3, less 4 Sheeis-Sheet 4 Fig: 4

Superhea fer 22m J'uperheafer 2 3 Uuile ATTORNEY.

Patented June 30, 1942 VAPOR GENERATOR Ralph M. Hardgrove, Westfield, N.J., and Robert K. Behr, Mount Vernon, N. Y., assignors to The Babcock &Wilcox Company, Newark, N. J., a corporation of New Jersey 7 ApplicationAugust 3, 1938, Serial No. 222,780

8 Claims.

This" invention relates to fluid heat exchange apparatus, and it will beconsidered as exemplified herein in a vapor generator. 7

The invention is more particularly concerned with vapor generatorsoperating at high pressures and high capacities. The vapor generators ofthe invention also involve the co-ordination of ,fuel burning and heatexchange apparatus capable of high rates of heat absorption at largetemperature differentials between the heat trans mitting products ofcombustion and the heat absorbing media.

In a high capacity steam power plant it is important that high overallefiiciencies be attained, and to attain such efficiencies, highpressures and high superheats are advantageous. ditions are usuallyaccompanied by high furnac gas temperatures.

In the central stations operating under the above conditions andutilizing steam for the development of electrical power, steam turbinesare usually employed. The steam. after passing through the turbines, iscondensed and returned to the steam generators so that relatively lowpercentages of make-up water are utilized.

Thus, the steam generators, or boilers, of such central stations arecontinuously using feed water of low concentration, and a minimum ofboiler foutage due to scaling, tube failures, etc., is experienced. I

Conditions are different in industrial installations in that suchinstallations are associated with demands for low pressure steam. Thesedemands are met by utilizing the steam exhausted from the prime mover atpressures above atmospheric. Consequently, the vapor generators usedThese conin such industrial installations are supplied with f feed watera high percentage of which is makeup.

The boiler of the present invention is particularly adapted forindustrial installations in which boiler feed water is almost 100%make-up, and with such a situation the boiler is required to operatewith boiler water having a relatively high concentration. In spite ofsuch conditions it operates at extremely high pressures and highsuperheats so as to attain high efiiciencies. Its steam generating partsare such. that they may be readily cleaned, and its furnace gasvelocities are low in order that adequate separation of suspended solidsmay be eiTected.

The invention is illustrated herein by preferred embodiments shown inthe drawings referred to in the following description, and other objectsgles to the plane of Fig.. 1, and on the line 2-2 of Fig. 1;

Fig. 3 is a vertical section through a boiler constituting anotherembodiment of the invention; and

Fig. 4 is a vertical section on the line 4--4 of Fig. 3, the plane ofthe Fig. 4 view being at right angles to the plane of Fig. 3.

The combustion chamber I0 of the Fig. 1 boiler is defined by water tubesconnected into the boiler circulation, and the spaces between thesewater tubes may be closed by refractory material secured to the tubesand forming the furnace faces.

The floor of the combustion chamber [0 is defined by floor tubes I2which are inclined downwardly toward the ash removal zone I4. Thesetubes are reversely bent at their lower portions and have their lowerends connected to a header I6 which receives water through externaldowncomers l8 connected to the water space of the drum 20. Water flowsupwardly through the tubes I2 to a lower wall header 22 and thenceupwardly through the wall tubes 24. These tubes discharge into theheader 26 which is connected to the drum 20 by the furnace roof tubes28. The headers, such as the headers l6 and 22, are all provided withhandholes so that tube cleaning tools can be directed into the connectedtubes.

The side of the combustion chamber opposite the tubes 24 is defined bythe wall tubes 30 which directly communicate with the drum 20 and aresuspended therefrom. These tubes, and the refractory material 32 securedthereto, form a division wall separating the combustion chamber l0 fromthe convection zone 34 in which the economizer 36 and a superheater arelocated. The wall tubes preferably act as supports for the superheatertubes at one side of the convection section.

The alternate division wall tubes 30 have their lower ends offset ormore-Widely spaced, providing two rows with alternative tubes instaggered relationship, as indicated at 40, so as to provide an outletfor the furnace gases passing from the combustion chamber III to theconvection zone 34. The tubes 30 receive water by reason of their Theside walls of the combustion chamber I are defined by wall tubes whichdirectly connect the lower headers 46 with the upper headers 48 and 50,the spaces between these tubes being closed by the refractory material52.

The furnace of the Fig. 1 boiler is fired by down-shot burners hereinindicated as the pulverized fuel burners 54 and 56, and the furnacegases after passing from the combustion chamber I0 to the outlet 40 passupwardly over the economizer and superheater tubes, through the Venturiconnection 80, and then across the tubes of the air heater 62. Themovement of the furnace gases through the air heater is indicated by thearrows 64, 66, and 68, while the air to be heated passes through thetubes I0 from the inlet I2 to the chamber I4. From this chamber the airpasses through the tubes I6 to the duct 18 and thence to the burners 54and 56.

The convection zone beyond the outlet 40 of the combustion chamber isdivided into three parallel gas passes 80, 82, and 84. The baflle 86separates the passes 82 and 84, while thepass 80 is separated from thepass 82 by the baflle 88.

In the gas passes 80 and 84 the tubes of a superheater are arranged. Ineach of these passes there is an upper counter-flow section indicated at90 and 92. Steam flowing generally downwardly through the tubes of thesesections passes to the lower portions of the parallel flow superheatersections 94 and 96, and then upwardly to the superheater outlet header88.

Feed water for the boiler enters the economizer inlet header I00 andthen flows through the coils I02 of the primary economizer across thegases flowing upwardly in the three gas passes 80, 82, and 84. Thissection of the economizer operates on counter-flow principles, the waterflowing through the coils I02 downwardly to the header I04 which is incommunication with the header I06 of the secondary economizer. Theconduit I08 establishes this communication. This secondary economizer isarranged in the gas pass 82 and between the superheater sectionspositioned in the adjoining gas passes. It operates on parallel flowprinciples, dis-charging water or steam and water directly from itsupper portion to the steam and water drum 20.

The gas pass 82 in which the secondary economizer is located constitutesa gas by-pass for the superheater, the proportioning of the furnace gasflow through this by-pass and over the superheater being accomplished bythe manipulation of gas flow controllers IIO, several of which are shownin Fig. 2 at the outlet ends of the parallel gas passes. Adjacentcontrollers preferably rotate in opposite directions in order toaccomplish a better throttling effect, and better control of thesuperheat.

The Fig. 1 boiler isof high efilciency and is particularly adaptedforoperation at the high fluid pressures which are required for the mosteflicient generation of power. Its operating pressure is in excess of2000 pounds per square inch.

When pulverized coal is used as fuel the limitation of the combustionrate with reference to the area of heat absorbing surface in sight offurnace radiation-is such that the ash is deposited on the floor in adry state. This heat absorbing surface, essentially in the form of watertubes for high pressure boilers, is most effective, and in the presentboiler it is desirable the furnace water walls in the interest of dryash removal and most effective cooling of the furnace gases, isadditionally important when the boiler operates with boiler water ofhigh concentration of solids.-

It is also to be noted that all of-tne steam generating tubes of theillustrative boiler are located in the walls of the furnace and in theadjoining gas pass. The heating surface thus provided, especially in thefurnace walls which are of sufficient area to insure dry ash, is as awhole also sufficient to generate substantially all of the steam thatthe furnace gases can superheat to the required degree at thecontemplated pressure. The economizer is located in the gas pass beyondthe superheater, preheating the feed water and possibly generating somesteam. There is no bank of convection steam generating tubes such as hasbeen usually considered standard in water tube steam boilers.

It is also tobe understood that at the very high pressures used and atthe pertinent superheat, the latent heat of vaporization is smaller inrelation to the heat of liquid heating and steam superheating than atlow pressures. It is enough smaller to make it possible to reduce thesteam generating surface and to concentrate all of it in the furnacewalls, especially when these walls have sufficient effective coolingarea to cause congealing of the molten ash and its deposit, orseparation, in dry form.

In the illustrative boiler the disposition of the steam generatingsurface in the walls of the furnace makes it unnecessary to provide suchsetting walls as have been a problem in the use of water tube steamboilers.

The arrangement of the superheater and economizer in the gas pass issuch as to provide for the control of superheat without loss ofefficiency. One section of the economizer extends across the whole widthof the gas flow through the entire convection section. It has anadvantageous downflow of water, while a second section of theeconomizer, with an upflow of water, extends between two verticalbaffles at the level of the superheater. The middle part of the gas passcontaining a part of the economizer is also a superheater by-pass toregulate superheat by damper gas control at the top of the gas pass.

In the embodiment of the invention illustrated in Fig. 3 of the drawingsa combustion chamber indicated generally by the numeral III has itsboundaries defined by steam generating tubes in a manner somewhatsimilar to that of the modification previously described. The floortubes I I2 slope downwardly toward the ash pit H4 and are covered ontheir furnace sides with refractory material H6. The upright wall tubesH8 and I20 may have the spaces between them filled with ceramicrefractory material held in place by metallic extensions welded to thetubes. These tubes are preferably bare on their furnace sides so as topromote a high degree of furnace gas cooling, and in an ignition zoneadjacent the burner I22 the tubes are entirely covered by ceramicrefractory material to promote high ignition temperatures. The ceramicrefractory covering on one wall in the ignition zone is indicated inFig. 3 by the area ABCD.

With reference to the Fig. 3 embodiment, it is to be noted that the ashpit H4 is beneath the convection zone I30 and that the extensions I32,

I34, and "61mg. 4) of the tubes I24 of the division wall separating thecombustion chamber from the convection zone extend downwardly from thedrum I to a position intermediate the roof and the wall of the furnace.From that position they extend laterally toward the remote the gasesfrom the furnace enter the convection zone only over a part of the widthof the installation. This is indicated by the distance between thebaflle I48 and the wall I60 in Fig. 4 of the drawings. the baifleextending above one edge of the refractory material I46 and the wall I50being defined by wall tubes I62 connecting the upper header I54 with thelower header I56. In the space between the wall I and the bailie I48 thegasespass over a screen formed by the downwardly inclined parts of thetubes I32 and I36. They then .pass upwardly over the'tubes of thesuperheater I60- and the tubes of the economizer I62 located in thesuperheater gas pass defined by the baifles I64- and I66.

The tubes of the superheater are in the form of flat coils partiallysupported by'the division wall tubes I24.

Steamfrom the drum I40 passes'through th saturated steam supply tubesI10 to the superheater inlet header I12'and thence generally downwardlythrough the flue I14 to the superheater outlet header I16.

The economizer may be considered as arranged in two sections. The firstsection I is a counter-flow section located in the flue I82 formed bythe baflie I64 and'the wall I84. In this section the feed water entersthe economizer inlet header I86 and proceeds upwardly through the tubesof the economizer section I80 to the intermediate header I88. Fromthisheader the feed water passes downwardly to the inlet header I90 of theparallel flow eaonomizer section in the gas pass 7 between the walls I64 and I66. From that headtop of the superheater by-pass.

er the fluid within the tubes passes upwardly to thefeconomizer outletheader I92 and thence to the drum I40.

Superheat control is attained bythe operation In addition to thedampercontrol of gas flow I through the superheater by-pass, Fig. 3 indicatesThe furnace gases after passing over the tubes of the counter-floweconomizer section pass around the lower end of the wall I84 upwardlythrough the idle pass 204 and then downwardly through the tubes 206 ofthe air heater 208. Thence they pass through the exhaust fan 2I0 andthrough a flue 2| 2 to a stack.

In the operation of the air heater, cold air passes from the inlet 2I3over the tubes 206 to the hot air outlet 2l4, and in order to preventcorrosion of the air heater tubes by condensation of the combustionproducts at low loads, some of the cold air from the inlet is permittedto pass directly to the outlet 2I4 through the conduit 2| 6, the amountof air thus by-passing the air heater tubes 206 being'determined by theoperation of the controller 220. When the quantity of air passing overthe tubes is reduced, the exit gas temperature from the air heater ishigher and condensation is avoided.

' said tubes extending across the furnace gas inlet 8 a plurality ofdampers 280 arranged across the top of the superheater so as to directlycontrol the gas flow thereover. Adjacent dampers 280 are arranged tomove in opposite directions when.

they are operated for the reason above referred toin describing theoperation of the damp.ers.

200 and 202.

We claim: A 1. In a water tube steam boiler, a furnace presenting acombustion chamber the sides of which are defined by wall'tubes whichenable the boiler to generate sufficient steam without the inclusion ofa natural circulation bank of steam generating tubes, a convectionsection including a superheater, means forming an ash disposal zonebeneath the convection section, means causing the gases to tum'upwardlyin passing from the combustion chamber and over said zone to theconvection section, means for dividing the convection section into aplurality of gas passes two of which lead upwardly in parallel from saidzone to the entrance of the third gas pass, horizontally inclined tubesections extending over said zone at a position beneath said gas passes,some of said tube sections acting as a gas mixing slag screen across theentrances of the parallel I I gas passes, refractory material closingthe spaces between others of' the tube sections to close off the thirdgas pass and form a baffle directing the gases laterally toward theparallel gas passes,

passes to control superheat, and means causing the gases to pass fromsaid parallel passes into said other gas pass.

2. In a water tube steam boiler, fluid heating and steam generatingtubes defining the walls and other boundaries of a combustion chamber,means for burning fuel in said chamber, substantially all of the'steamgenerated by the boiler being generated as a result of the radianttransmission of heat to said tubes, other tubes connected into theboiler circulation and co-operating with some of the first mentionedtubes to define a convection heating zone to and through which furnacegases pass from the combustion chamber, economizer and superheaterelements supported by the tubes defining the convection zone, saidelements extending across the furnace gas flow, and means forming an ashcollection zone common to the combustion chamber and the convection zonefor the disposal of the solid residues of combustion, some of said tubesdefining floor surfaces of the combustion chamber and the convectionzone downwardly inclined toward the common collection zone and others ofthe tubes constituting agas mixing screen at a position above thecollection zone and between the combustion chamber and the convectionzone. 3. In fluid heat exchange apparatus, fluid heating tubes defininga combustion chamber having a gas outlet at the lower part thereof,means forming a gas pass in which the furnace gases pass upwardly fromsaid outlet, some of of said gas pass, means dividing said gas pass intotwo parallel gas passes immediately beyond said inlet, a secondaryeconomizer in one of said parallel passes, a superheater in the other ofsaid parallel passes, means for controlling the division of the totalfurnace gas flow between the parallel passes to control superheat, and aprimary economizer subjected to all of the furnace gases beyond saidparallel passes.

4. In a steam generator, a boiler setting, furnace wall tubes defining acombustion chamber having a furnace gas outlet at the lowerpart thereof,a steam and water drum in communication with said wall tubes, other walltubes in communication with the drum and defining a wall of a secondstage furnace gas chamber receiving the furnace gases from said outlet,some ofsaid first mentioned wall tubes having parts defining a walldividing the combustion chamber from the second stage chamber and otherparts constituting a screen extending across said outlet, fuel burningmeans associated with the combustion chamber, means providing aplurality of gas passes arranged in parallel in the second stagechamber, said gas passes receiving the furnace gases from the combustionchamber, steam generator auxiliary in the respective parallel passes,means for controlling the division of the furnace gases between saidpasses to regulate the effect of at least one of said auxiliaries, and

means forming a reverse gas pass within the setting, said reverse gaspass being arranged to receive furnace gases discharged from both ofsaid parallel passes.

5. In a steam generator, a combustion chamber, a convection section inwhich spaced tubes extend across the path of the furnace gases from thecombustion chamber, spaced tubes connected into the fluid system of thegenerator and defining a division wall between the combustion chamberand the convection section, said tubes having lower portions disposedbeneath the convection section, the lower portions of some of the tubesbeing arranged in wall alignment while the remainder are arranged as ascreen across the furnace gas inlet of the convection section,refractory material filling the spaces between the tubes which are inwall alignment, and a baffle construction, extending upwardly from saidwall aligned tubes and, into the convection section to direct thefurnace gases over the tubes of the convection section above the screen.

6. In a steam generator, a boiler setting of rectangular section, afurnace, walls of which are defined by steam generating tubes, down-shotpulverized fuel burners firing the furnace, a convection sectionlaterally adjacent the furnace, some of the steam generating tubesdefining a division wall comma to the gas pass of the convection sectionand he furnace and having their lower ends bent so *as to extend inscreen formation across the gas entrance to the convection section,fluid heating tubular elements extending transversely of gas fiow in theconvection section, the said heating elements being partly supported bythe division wall tubes, means providing water cooled fioor surface forthe bottom of the furnace area and extendin eneath theconvection sectionfor the disposal of-ash particles thereof, the furnace wall tubes andthe partition tubes being connected to an upper steam and water drumextending transversely at a position across the central portion of thesetting.

7. In a steam generator, a boiler setting of rectangular section, afurnace, walls of which are defined {-by steam generating tubes,down-shot pulverized fuel burners firing the furnace, aconvectionsection laterally adjacent the furnace, some of the steamgenerating tubes defining a wall directly dividing the gas pass of theconvection section from'the furnace and having their lower ends bent soas to extend in screen formation across the gas entrance to theconvection section, superheater elements extending transversely of gasfiow in the convection section, the said superheater elements beingpartly supported by the division wall tubes, means providing watercooled surface for the bottom of the furnace area and extending beneaththe convection section to form the wall of an ash disposal zone, thefurnace wall tubes and the partition tubes being connected to an uppersteam and water drum extending transversely at aposition across thecentral portion of the setting, means connecting the steam space of thedrum with the superheater elements, the superheater elements beingU-shaped straight portions extending throughout the major portions oftheir length and transversely of the gas flow.

8. In a steam generator, a boiler setting of rectangular section, afurnace, walls of which are defined by steam generating tubes, down-shotpulverized fuel burners firing the furnace, a convection sectionlaterally adjacent the furnace, some of the steam generating tubesdefining a partition wall directly dividing the gas pass of theconvection section from the furnace and having their lower ends bent soas to extend in screen formation across the gas entrance to theconvection section, superheater elements extending transversely of gasflow in the convection section, the said superheater elements beingpartly supported by the division wall tubes, means providing watercooled surface for the bottom of the furnace area and extending beneaththe convection section for the disposal of ash particles thereof, thefurnace wall tubes and the partition tubes being connected to an uppersteam and water drum extending transversely at a position across thecentral portion of the setting, means connecting the steam space of thedrum with the superheater elements, the superheater elements beingU-shaped with straight portions extending throughout the major portionsof their length and transversely of the gas flow, the screen extensionsof the partition wall tubes having their lower ends extending verticallyalong a downward extension of a wall of the convection section.

RALPH M. HARDGROVE. ROBERT K, BEHR.

CERTIFICATE OF CORRECTION. Patent No. 2,287,798. June 50, 19142.

RALPH M. HARDGROVE, ET AL.

It is hereby certified that error appe'arsin the printed specificationof the above numbered patent requiring correction as follows: Page 1,secand column, line 51, for the word "alternative" read -alternate--;page 14., first column, line 21, claim L for "auxiliary" read--auxi1iaries--; line 11.5, claim 5, strike out the comma after"construction"; and second column, line 28, claim 7,before "straight"insert with-- ;and that the said Letters Patent should'be read with thiscorrection therein that the same may conform to the record-oi the casein the Patent Office.

Signed and sealed this 15th day-of August, A. D. 19%.

Leslie Frazer (Seal) Acting Commissioner of Patents.

